bolex h16 problem

I'm worried about my bolex. When firing a single frame in the mode where the shutter stays open as long as you hold the switch, the shutter doesn't appear to be completely clear of the gate. I just realized this after shooting 600' for my term final!

Does this sound as if all my film will definitely have a big black slash across each frame? Could it be an issue that only occurs during single frame exposure?

You have a shutter timing problem ... If its only slightly across the gate you maybe ok as there is a small pause between the shutter and the claw pull-down action

When the camera runs normally the shutter wont stop like it does in single frame mode, hence you wont see a shadow like you were suggesting - however, worst case scenario (assuming you were shooting with the shutter fully open) - you will have a vertical smear in your highlights ...

I actually took the camera in for service today, along with a rex4 I had which also needed service. Instead of leaving with two fixed rex's, I ended up leaving with a beautifully clean super16 EBM full kit w/nikon mount, powergrip and battery!